The following remarks deal with the problems which native speakers of Spanish are likely to experience with the English vowels. The type of English referred to is the General British pronunciation (“GB”) and not the General American variety from which it has a small number of notable differences.
1. The GB vowel / i: / as in seat should give no qualitative problems but it may sometimes be made in forms inappropriately brief and yet occasionally excessively stretched. It is usually, but by no means always, a fairly long vowel so that, given the typically short value of the qualitatively comparable Spanish vowel, it may sound markedly brisk or clipped and possibly uncomfortably like the more regularly short English vowel phoneme / ɪ /, as when eg seat may sound too much like sit. The context in which it is desirable to give / i: / its minimum length is in a syllable which is closed by one or more of the eight “sharp” (aka 'voiceless' or 'fortis') English consonants /p, t, k, ʧ, f, θ, s / and / ʃ /.
1b. The weak vowel / i /, the final vowel in city and easy, should give no problems if it is not made strong (and thereby long). In America very widely and in Australasia universally there is extensive use of / i: / instead of / i / in such final syllables.
2. The GB vowel / ɪ / as in sit has no precise equivalent in Spanish and is therefore very likely to be attempted in a form too much like /i:/, making eg sit sound too much like seat. As diagrams show, it's as near (in position and therefore in quality) to /ə / as to /i:/.
Diagrams for GB vowels and diphthongs may be seen at §3.1.46 and for Spanish vowels at §9.2 on this website.
3. The GB vowel /e/, as in leg , should give little or no trouble.
4. The GB vowel / ӕ / as in hat is today for most British speakers about the same sort of vowel as is represented in the spelling of Spanish by the letter a. A small minority of older British speakers and many Americans and Australians etc have values of / ӕ / much nearer to / e /. Spanish speakers will have to be careful not to produce it without sufficient differentiation from / ᴧ / from which it now differs so little that British native English speakers sometimes mistake each other’s intentions in regard to it.
5. The GB vowel / ɑː / as in arm or calm is likely to be attempted with a quality that too much suggests a drawled / ӕ / because the tongue has not been drawn back far enough in its production. It is usually a fairly long vowel except before sharp (aka voiceless etc) consonants.
6. The GB vowel / ɒ / as in got sometimes tends to be attempted with too much rounding of the lips and with such a high tongue position that it is not sufficiently differentiated from the vowel / ɔː /.
7. The GB vowel / ɔː / as in saw should give no difficulty so long as it is made fairly long without submitting it to any degree of diphthongisation which would cause it to sound too much like / ˈɔːu / or / əʊ /.
8. The GB vowel / ʊ / as in put has no precise equivalent in Spanish and is therefore very likely to be attempted in a form too much like / u: / but, as diagrams show, it's as near (in position and therefore in quality) to /ə/ as to / u: /. Saying / ə / with rounded lips should help to produce a satisfactory / ʊ /.
9. The GB vowel / u: / as in too should give no qualitative problems but it may sometimes be uttered in inappropriately brief (or very occasionally excessively stretched) forms. It is usually a fairly long vowel so that, given the typically short value of the qualitatively comparable Spanish vowel, it may sound markedly brisk or clipped and uncomfortably like the more regularly short English vowel phoneme / ʊ /, as when eg soot may sound too much like suit. It has its minimum length in syllables closed by one or more of the sharp consonants.
9b. The weak vowel /u/, the final vowel in eg cuckoo, w and Zulu, should give no problems if it is not made strong (and thereby long). It is commonly replaced by the corresponding strong vowel in various other forms of English.
10. The GB vowel / ᴧ / as in cup has a higher and more back tongue posture than Spanish / a /.
11. The GB vowel / ɜː / as in fur is never very short or it would be indistinguishable from / ə / with which it shares its very neutral “obscure” or indeterminate quality. Spanish speakers may make this vowel too forward and therefore too much like / e / or / eə /.
12. The GB vowel / ə / is often wrongly described as
never occurring in stressed syllables though it is quite true that only
a very few words have it stressed and none of those invariably so. It
is often stressed in the adverb just (but not in the adjective) and in
the first syllable of threepenny etc. Students are best advised never to stress it.
13. The GB diphthong / eɪ / as in page has a Spanish equivalent so that it should give no trouble if sufficiently short notably before sharp consonants.
14. The GB diphthong / əʊ / as in go is rather different from the Spanish diphthong ou. If not begun fairly centrally it may sound abnormal and too like / ˈɔːu /.
15. The GB diphthong / aɪ / as in five, if not begun fairly front, may sound abnormal or too like / ˈɑːi /.
16. The GB diphthong / aʊ / as in now, if not begun front enough may sound abnormal or too like / ˈɑːu /.
When either of the last two diphthongs is followed by a schwa to give / aɪə, aʊə / in such words as fire and hour, the result is often a single syllable with weakening of the middle sound which usually disappears altogether in unstressed syllables as in empire or rushhour.
17. The GB diphthong / ɔɪ / as in join is rarely problematical.
All the above diphthongs are usually fairly long but care must be taken to reduce them when they are followed by sharp consonants or enclitic syllables (ones which are, or behave as if they were, further unstressed syllables of the same word). Failure to do so will produce the effect of making inappropriate word divisions eg instead of joking saying Joe King.
18. The GB diphthong / ɪə /as in near if not begun with a sufficiently central quality may strike many British speakers as abnormal and too like / i:ə / though that's not very likely to cause any misunderstanding.
19. The GB diphthong / eə / as in hair may be begun too high producing the effect of / eɪə / as in player though that's not very likely to cause any misunderstanding. By a high proportion of GB speakers it's regularly made as a long simple vowel [ɛː] so students may aim for this value if they prefer. This latter smoothed value is used by almost all speakers unless stressed and immediately before a break in rhythm.
20. The GB diphthong / ʊə /as in cure, if not begun with a sufficiently central quality, may strike many British speakers as too much like / ˈu:ə / as in queuer, sewer, fewer or doer though that's not very likely to cause any misunderstanding. Like / eə / it has most often its smoothed version [ʊː] unless it's stressed and comes immediately before a break in rhythm.
1. Although vowel values may be strikingly different in one part of the English-speaking world from what they are in another, the same system of consonants will be found among virtually all educated native speakers of English worldwide. Millions of unsophisticated speakers in eg London, New York and Dublin have no / θ / or / ð / but this is strictly limited to low-prestige varieties of English. On the other hand, inhabitants of the Celtic countries (ie Wales, Scotland and Ireland) usually employ a [x], ie the same sound as a Spanish jota, in various regional names and terms. Compare the Scottish English version of loch which ends with /x/. The usual GB form of the word has as final consonant /k/.
2. The English inventory of consonants consists of 24 units (phonemes) which can usefully be considered in three sets of eight items each. Two of the sets are very closely parallel because each item in them differs from its corresponding member of the other set essentially only by whether its articulation is (ordinarily relatively) sharp or soft. The remaining set of eight is more miscellaneous.
3. Some eight of these, viz / f, θ, s, ʧ, m, n, j / and /w/, correspond very closely to phonemes occurring in the Spanish language. Others can be said not to exist in Spanish, at least in Castilian, eg /ʃ/ and /ʤ/; but as regards most of the remaining items, the contrasts between the two languages are more complex.
4. The 20 Spanish consonantal phonemes include five types /x, ɲ, ʎ, rr/ and /ɾ/ not found in English.
5. English /p/ differs from Spanish /p/ in quality chiefly by virtue of being subject to what is known as “aspiration” ie it is always followed by a marked short burst of air (of /h/ quality) whenever it begins a stressed syllable and sometimes less noticeably by a slighter puff in other situations. This is important because it is what keeps /p/ & /b/, /t/ & /d/ and k/ & /g/ apart in English. Hearing the Spanish word pacharan for the first time I wrote it as bacharan which is a fact that should warn students that if they fail to aspirate stressed syllable-initial /p/ etc, a native English speaker will be very likely to interpret that attempt at /p/ etc as the correspnding soft (voiced) consonant. By contrast, it is mainly because Spanish /b/ has voicing (accompanying vibration of the vocal folds) that it is distinct from Spanish /p/. The same pattern of aspiration versus non aspiration applies less obviously to English / ʧ / and / ʤ /, the sounds respectively at the beginnings and the ends of church and judge.
6. The letters b and v in English ordinarily
represent quite distinct sound units of the language. On the contrary,
for Spanish they are merely variant spellings for the same phoneme. In
English /b/ is regularly a bilabial plosive while /v/ is typically a
labiodental fricative. The Spanish phoneme on the other hand is
variously a bilabial plosive or fricative or approximant sound.
7. The approximant allophone (variant) of the Spanish b/v sound differs from English /w/ only by lacking lip-rounding. Such a sound may be heard from English speakers when, as is quite often the case in rather hurried articulation, the word able is pronounced as [eɪβl]. The utterance-initial plosive sometimes substituted by Spanish speakers for an English fricative (or approximant or rarely plosive) /v/ can disguise a word eg make the word very sound like beret.
8. The English consonant /ð/ corresponds in sound quality exactly to the Spanish d at the ends of words or within them but adjacent to an /n/ or /l/ the Spanish phoneme takes a plosive form like English /d/. So Spanish speakers have to be particularly careful not to substitute /d/ for initial th - when saying eg in that, on the, when they, although, tell them etc.
9. The sound quality of the English /s/ as attempted by some Spanish speakers is rather too similar to the English sh sound /ʃ/. Such a value is very occasionally heard as an idiosyncrasy from some British and some American speakers (eg the American James Stewart and the British Lord William Deedes) but it should certainly be avoided by Spanish-speaking learners.
10. The buzzing sound quality of the English /z/ is only heard in (Castilian) Spanish as an allophonic variant value of the letter s in a word like mismo. It sounds totally abnormal to produce a /z/ instead of an /s/ at the beginnings of English words like slow, small, snap etc.
11. English /ʃ/ as in she, / ʒ / as in pleasure and /ʤ/ as in judge do not have equivalent phonemes in (Castilian) Spanish so care must be taken not to confuse /ʃ/and /ʧ/ as in washing versus watching etc and not to substitute /ʧ/ for any of them.
12. All four of / ʧ , ʤ , ʃ /and / ʒ / are markedly rounded in English: Spanish speakers occasionally fail to make them rounded enough especially in palatal contexts eg as in cheap, cheese and chin.
13. The English type of aspirate /h/ as in how does not occur in Castilian. English /h/ is normally a very weak sound and any attempt at it which resembles the Spanish speaker’s jota [x] will be likely to sound very harsh, as would any use of the typical strongly fricative Spanish value of non-initial g [ ɣ ].
14. English / m /as in mum corresponds exactly to Spanish /m/. However, although all three of the English nasal phonemes /m, n, ŋ/ may end syllables, only /n/ of the three Spanish nasal phonemes /m, n, ɲ / may do so. This is reflected in the fact that Biblical names such as Abraham, Adam, Bethlehem (Spanish Belén), Jerusalem etc end in n in their Spanish forms. It is also no doubt responsible for the to-English-ears-alarming way in which many Spanish speakers (perhaps especially in Andalucia) seem to have an any-nasal-will-do approach to English words ending with /n/ like in and on etc.
15. English / ŋ /as in sing does not occur as an independent sound in Spanish though it does occur as an “accidental” value (an allophone) of Spanish /n/ under the influence of a following /k/, /g/ or /x/. It is naturally quite difficult for Spanish speakers to produce an / ŋ /which is not in such a context, especially in fluent speech when it occurs, as it so often does, in the very frequent unstressed word ending -ing. However, it deserves careful attention because failure can sound quite odd. The expression huntin’, shootin’ and fishin’ is well known in joking reference to an upper-class Victorian style of speech but is now associated either with persons of very little education or with elderly aristocrats.
16. English /l/ as produced by Spanish speakers is very unlikely to occasion failure to recognise words but it is noteworthy that English has variations in the precise quality of /l/ that are not parallelled in Castilian. (Catalan has some rather dark varieties though not with the English pattern of their distribution.) It is usual for GB speakers to produce a “darker” ie more back (meaning tongue-retracted ie velarised or pharyngalised) version above all when /l/ is syllabic but also when it occurs before consonants or word-finally. A minority have a neutral rather than a dark /l/ (centralised) but to have a really light (palatalised) value is to sound quite abnormal.
The English dark variety usually has a quality quite like that of the vowel / ʊ / so that eg eatable may sound from many native English speakers quite indistinguishable from `eat a bull. Some British speakers, chiefly those with a London tinge to their speech, tend to replace word-final syllabic /l/ with /ʊ/ so that eatable becomes /`i:təbʊ/. This is often not noticed by other British native speakers but students are best advised not to adopt it.
17. The English /r/ is typically an altogether weaker
and softer sound than the Spanish values for the letter r. It is
identified in phonetic terminology by the term 'postalveolar
approximant'. The sound of a single Spanish r between vowels is
completely regularly an alveolar tap. When word-initial or word-final,
it may also be an alveolar trill, which is what is always the value of
a Spanish rr.
A witness to the extreme weakness of the English /r/ is the fact that our traditional spelling has very numerous r's no longer pronounced by most speakers in Britain, about a third of US speakers and practically all South Africans and Australasians. Very large numbers of GB speakers omit eg the first /r/ from common words like prescription and program without anyone noticing the fact — not even pronunciation lexicographers. The retention of most of the r's of the traditional spelling by GA speakers is the biggest single difference between GB and GA.
18. Although Spanish has fairly exactly corresponding phonemes to English /j/ and /w/, there is hardly any tendency among English speakers to tighten their articulations of these phonemes in the way Spanish speakers often do when using English — making yes sound like Jess or "What whisky d’you want" sound like "Gwot gwisky do you gwont".
19. A well-known problem for Spanish speakers is occasioned by the fact that Spanish has no word-initial consonant clusters of the types /sl-, sm-, sn-, sp-, st-, sk-/. With these the tendency is to add an extra syllable to words containing them as with the Spanish borrowing from English of the word slogan which becomes [ez`logan] — in this case with an un-English assimilation [s → z] as well. Compare the treatments of other borrowings from English into Spanish eg Scotch, slip, slot, smoking, snob, sport, spot, stop, starter etc.
20. Various other cluster simplifications and elisions of consonants are also to be heard in Spanish speakers’ English at times eg as when one not too proficient speaker was reported as using an expression “Oss Forestry” which turned out to be an attempt at saying “Oxford Street”. It is important to remember that, although Spanish initial ex- can be reduced to /es-/ without causing consternation, to omit /k/ from English initial ex- tends to sound embarrassingly uneducated.
21. Speakers with a Catalan background should be always careful to avoid converting word-final soft consonants eg /b, d, g, v, z/ etc into the corresponding sharp ones /p, t, k, f, s/ etc.
Recommended further reading: A Course in English Phonetics for Spanish Speakers by D. F. Finch & H. Ortiz Lira. English Phonetics and Phonology for Spanish Speakers by Brian Mott.